Fanconi Anemia (FA) is an autosomal recessive disease characterized by progressive bone marrow failure, cancer susceptibility, and multiple congenital abnormalities. Cells from patients with FA are hypersensitive to DNA-damaging agents, and the molecular defect is presumably one of DNA repair. While FA is a rare disease, acquired (somatic) mutations in FA genes could account for the genomic instability observed in primary cancer cells from patients in the general population. FA has at least eight complementation groups (A-H), and two FA genes, corresponding to complementation groups A and C, have been cloned and published. A third FA gene, for FA-G, has also been cloned, and will soon be published. We have recently demonstrated that the FAA and FAC proteins bind and form a nuclear complex, although the function of this complex remains unknown. Using the cDNAs for FAA, FAC, and FAG, specific antisera for FAA, FAC, and FAG proteins, and patient-derived cell lines from all eight complementation groups, we plan to continue our study of the molecular pathogenesis of FA. In Project I, during the five year study period, we will characterize several new FA cell lines and will perform a structure/function analysis of the FAA protein in order to further delineate its carboxy-terminal functional domain. In Project II, we will examine the role of FAA phosphorylation in FAA/FAC binding and FAA nuclear accumulation. Finally, in Project III, we will identify and clone additional proteins in the FAA/FAC protein complex in order to determine the nuclear function of the proteins. Newly-identified FA proteins, such as the FAG protein, will be tested for their presence in the FA protein complex. For this specific aim, we will also test the nuclear FA protein complex for direct in vitro DNA binding activity or DNA repair activity, using model DNA templates.